1. Field of the Invention
This invention relates to isocyanates and intermediates therefor and is more particularly concerned with isocyanatophthalic anhydride, intermediates therefor, and derivatives and polymers produced therefrom.
2. Description of the Prior Art
The 4-azidocarbonyl- and 4-isocyanatophthalic anhydrides, and the lower-alkyl carbamates of the latter, described herein are believed to be novel and applicants are not aware of any pertinent prior art.
Polyimides, closely related to those which are prepared as described hereinafter, are disclosed in U.S. Pat. No. 3,503,928 as being prepared by self-polymerization of 4-aminophthalic anhydride.